In a semiconductor manufacturing process, a solid or liquid semiconductor material is vaporized using a bubbling system, and the vaporized material gas is introduced into a vacuum chamber or the like.
The bubbling system includes: a tank adapted to contain the semiconductor material, an introduction pipe adapted to introduce carrier gas into the tank; and a lead-out pipe adapted to lead out mixed gas containing the carrier gas from the tank and the material gas resulting from the vaporization of the semiconductor material.
The performance and/or quality of semiconductor devices to be manufactured are affected by the concentration of the material gas in the mixed gas introduced into the vacuum chamber. For this reason, the concentration of the material gas in the mixed gas is measured by a concentration meter of some type such as an ultrasonic type or a non-dispersive infrared absorption (NDIR) type provided in the lead-out pipe, and concentration control is performed with a valve provided in the lead-out pipe so as to keep the measured concentration constant at a predetermined value (see Patent Literature 1).
Meanwhile, in the past, relatively stable semiconductor materials such as TEOS have been bubbled and thereby vaporized. However, it is necessary to deposit compound semiconductors in an LED process or a leading-edge Si semiconductor process, and therefore unstable semiconductor materials that include organic metals and easily decompose are also currently used.
For example, in the case where the material gas self-decomposes in the lead-out pipe, a material of a type that is not originally intended is introduced to the vacuum chamber, which may have some effect on the performance and/or quality of semiconductor devices to be manufactured.
Also, the concentration measured by the concentration meter is based on the premise that the mixed gas is configured to contain only the carrier gas and the material gas, and therefore if another material is produced by the self-decomposition of the material gas, errors may occur in concentration measurement and concentration control.